1. Field
An embodiment of the present invention relates to an optical integrator system, an illumination optical apparatus, an exposure apparatus, and a device manufacturing method. More particularly, an embodiment of the present invention relates to an optical integrator system applicable to illumination optical apparatus in exposure apparatus for manufacturing devices (electronic devices and others) such as semiconductor devices, imaging devices, liquid-crystal display devices, and thin-film magnetic heads by lithography.
2. Description of the Related Art
In an exposure apparatus, a beam emitted from a light source is incident to a fly's eye lens as an optical integrator to form a secondary light source consisting of a large number of light sources on the rear focal plane of the fly's eye lens. Beams from the secondary light source travel through an aperture stop and a condenser lens to illuminate a mask with a predetermined pattern in a superimposed manner. Light having passed through the pattern of the mask travels through a projection optical system to be focused on a wafer. In this manner the mask pattern is projected (or transferred) onto the wafer to effect projection exposure thereof.
For example, a cylindrical micro fly's eye lens comprising a pair of fly's eye members having cylindrical lens groups formed on their two side faces is disclosed as an optical integrator capable of keeping down influence on the illuminance distribution from manufacturing errors in the large number of microscopic refracting surfaces integrally formed by etching in Japanese Patent Application Laid-open No. 2004-198748.